Keratotome for performing arcuate incisions

ABSTRACT

The present invention relates to a keratotome for forming arcuate incisions in a cornea for the purpose of correcting astigmatism. To this end, the keratotome (3) comprises a tubular outer support (4) containing a tubular inner body (6) that is capable of rotating relative thereto and that in turn contains at least one blade (82) capable of projecting by a predetermined amount relative to a reference surface (13) whereby the tubular outer support (4) bears against the cornea (2). In order to make arcuate incisions of determined angular position and of determined angular length, the support (4) and the body (6) have means (108) for determining their relative angular position.

The present invention relates to a keratotome for performing arcuateincisions in a cornea in order to correct astigmatism.

BACKGROUND OF THE INVENTION

Astigmatism in an eye is the result of two mutually perpendicularmeridians of the anterior face of the cornea not having the samecurvature, and a known method of correcting astigmatism consists informing two incisions in the cornea perpendicularly to the most highlycurved meridian, i.e. to the meridian with the shorter radius ofcurvature, said two incisions being disposed respectively on oppositesides of the optical zone.

Merlin ("Curved keratotomy procedure for congenital astigmatism";Journal of Refractive Surgery, 1987; 3:92-97) has made arcuate incisionsfor the purpose of correcting astigmatism, by using a micrometer bladeheld manually while using visual guidance based on a mark previouslymade by means of a circular marker.

Nevertheless, it is difficult to make incisions of uniform depth bymeans of a blade that is merely held in the hand, and this isparticularly true when said incisions are situated on a diameter that issmall.

As a result, such arcuate incisions are little used.

An object of the present invention is to make it possible to formarcuate incisions that are sufficiently accurate to achieve resultsregardless of the dexterity of the surgeon.

SUMMARY OF THE INVENTION

The present invention seeks to solve the stated object by mechanicalmeans and, to this end, it provides a keratotome for making an incisionin a cornea and comprising, for this purpose, in conventional manner forkeratoplasty trephines:

an envelope-forming tubular outer support having a determined axis andincluding, for application against a cornea, an annular base portionthat is circularly symmetrical about the axis of the support and thatdefines a reference geometrical surface determined by the shapepresented by the cornea when the support has its base portion pressedthereagainst;

a tubular inner body disposed coaxially inside the support and set backtowards the inside of the support relative to the reference surface;

guide means for guiding the body in rotation about the axis relative tothe support;

drive means for driving the body in rotation about the axis relative tothe support;

a blade disposed inside the body and extending along a longitudinaldirection, the blade having a sharp tip in a determined directionrelative to its longitudinal direction; and

means for providing a connection between the blade and the body, saidmeans including means for displacing the blade in controlled manner intranslation along its longitudinal axis relative to the body between arest position, in which it is set back towards the inside of the supportrelative to the reference surface, and in which the tip is directedtowards said reference surface, and in a cutting position where the tipprojects outside from the support relative to the reference surface, ina manner that is offset relative to the axis of the support;

characterized in that in order to perform arcuate incisions ofdetermined angular position and of determined angular length, thesupport and the body have determining means for determining theirrelative angular position.

It will readily be understood that such a keratotome makes it possibleto make incisions that are exactly in the form of a circular arc, and asa result that relate to a zone in which the cornea is of substantiallyconstant thickness, and also makes it possible, without difficulty, tocontrol two important parameters, namely the angular length of theincision, and the depth of the incision which is adjusted by adjustingthe extent to which the tip of the blade projects out from the body,when in the cutting position.

Other characteristics and advantages of a keratotome of the inventionappear from the following description of a non-limiting embodimentdescribed with reference to the accompanying drawings which form anintegral part of the present description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a keratotome of the invention, half in side elevation andhalf in section on a plane marked I--I in FIG. 2, and including therelative axis of rotation between the inner body and the outer support,which axis coincides with the visual axis while the keratotome is inuse.

FIG. 2 is a fragmentary plan view of the keratotome, i.e. it shows thekeratotome as it appears at its end opposite from its base portion,parallel to the axis of relative rotation between the inner body and theouter support and in the direction marked by arrow II in FIG. 1; forreasons of clarity, the blades and the blade carriers are omitted fromthis figure, as is the detail of the means for driving the body torotate relative to the support.

FIG. 3 is a view of a ring carried by the support, and shown in sectionon two half-planes that include the axis of relative rotation betweenthe inner body and the outer support, and marked III--III in FIG. 2, theangular position of the ring being adjustable about the axis of relativerotation between the body and the support and the ring itself carryingthe abutments provided on the support for limiting rotation of the body.

FIG. 4 is a section on a plane including the axis of rotation betweenthe body and the supports, such as the plane I--I of FIG. 2, and shows afirst embodiment of means for marking the position of the keratotomerelative to the cornea.

FIG. 5 shows the same means in plan view, e.g. as seen in the directionmarked by arrow II in FIG. 1.

FIGS. 6 and 7 are respectively a plan view as seen in the directionmarked by arrow II in FIG. 1 and a section view on the plane markedIX--IX in FIG. 2 and including the axis of rotation of the body, showingthe means for marking the astigmatism axis.

FIG. 8 is a view as seen in the direction of arrow X in FIG. 1, showinga detail of the micrometer means for separating respective zones of theblade carrier and of the body, thereby enabling the extent to which thetip of a blade is offset relative to the axis of relative rotationbetween the body and the support.

FIG. 9 shows a detail view of a blade as seen in the direction marked byarrow XI in FIG. 1.

FIG. 10 is a view in the direction marked by arrow XII in FIG. 1 showinga detail of the means for displacing the blade adjustably in translationalong its own direction, i.e. for adjusting the extent to which the tipof the blade projects out from the support relative to the referencesurface when the blade is in its cutting position.

FIG. 11 shows a portion of FIG. 1 on a larger scale.

DESCRIPTION OF PREFERRED EMBODIMENTS

The keratotome shown is of a type comprising two blades, but it willnaturally be understood that providing a keratotome having only oneblade or possibly have more than two blades would not go beyond theambit of the present invention.

For the purpose of being grasped in the hand of the surgeon and forenabling it to be positioned on the anterior face 1 of the cornea 2 tobe incised, the keratotome shown 3 includes an outer support 4 which isgenerally in the form of a tubular frustoconical wall that issymmetrical about an axis 5 and that surrounds an inner body or carriage6 which is also in the form of a tubular wall that is symmetrical aboutthe axis 5 and that is rotatably mounted inside the support about saidaxis 5, with any other type of relative displacement therebetween beingprevented.

The outer support 4 flares from a base portion 7 that is intended to bepressed against the anterior face 1 of the cornea 2 to be incised,around the location of the incisions to be made, and it extends to ahead portion 8 that is intended to be held by the non-dominant hand ofthe surgeon.

The wall constituting the base portion 7 of the outer support 4 includesan annular cavity 9 that is circularly symmetrical about the axis 5 andthat opens out into the base portion 7 via an annular slot 10 which isdefined between two annular bearing surfaces 11 and 12 that arecircularly symmetrical about the axis 5 and that lie on the samereference surface 13. The reference surface 13 is chosen to correspondwith the anterior face 1 of most corneas 2. A suction effect towards theinside of the cavity 9 is provided through the slot 10 by connectingsaid cavity 9 to means 14 suitable for establishing a reduced pressuretherein, said means being connected to the cavity 9 by a coupling 15therefor on the outside of the support 4, and by a flexible hose 16.

The bearing surface 11 closer to the axis 5 is preferably constituted byan annular part 17 rotatably mounted on the support 4 in an annulargroove 18 thereof facing the axis 5. This groove is delimited by twodismountable parts so as to enable the part 17 shown in FIGS. 1, 4, and5 to be changed.

The part 17, or any other part that may be substituted therefor,comprises a peripheral skirt 20, 21 that constitutes a circularlysymmetrical annulus about the axis 5 that is closely complementary inshape to the shape of the groove 18. Inside the skirt 20 or 21, the part17 has a wall delimited by a plane top face 22, 23 perpendicular to theaxis 5, and having determined shapes on its other face lying flush withthe reference surface 13.

Thus, as shown more particularly in FIGS. 4 and 5, the part 17 has atransverse wall in the form of a ring 24 delimited by two plane faces 22and 25, and by an annular edge 26. Four zones 27 disposed on the samegeometrical cylindrical (not referenced) of radius R₁, and of angularextent α₁ close to 90°, alternate with four zones 28 of angular extentα₂ of the order of a few degrees. Each of these zones 28 carries an edge29 on its face 25, said edge being an arc of a circle 30 of radius R₂smaller than R₁ and, in practice, greater than the radius of thetransparent zone of the cornea.

The four edges 29 enable the keratotome 3 to be accurately placed on thecornea 2 after the cornea has previously been marked with circlescentered on the visual axis. The four edges 29 lie flush with thereference surface 13 and together they constitute the bearing surface 11that comes into contact with the anterior face 1 of the cornea 2 on thecircular markings having the same radius as the circle 30.

The part 17 may also include, projecting from its face 25 in theimmediate proximity of each edge, a group of teeth 31 that prevent thekeratotome from sliding over the anterior face 1 of the cornea. The part17 is also completely situated in a position that is set back relativeto the reference surface 13.

The outer support 4 includes another internal annular groove 39 in itshead zone 8, having a bottom 40 of diameter that is as large as possiblegiven the dimensions of the head portion 8. The groove 39 includes twoplane flanks 41 and 42 perpendicular to the axis 5. The flanks 41 and 42open out onto respective faces 43 and 44 of the outer support 4, whichfaces are circularly symmetrical cylinders about the axis 5 which theyface, directly in the case of the flank 42 and via a rim 45 in the caseof the flank 41. Beneath the face 43, the support 4 includes a taperingface 46 that converges towards its base portion 7. The outer support 4is delimited at its top by a plane face 47.

The above-described support 4 is advantageously made up of a pluralityof parts that are assembled together by means enabling them to be takenapart at will, thereby enabling the support to be cleaned easily. Inparticular, the head portion 8 and the base portion 7, although they aresecured to each other, can be taken apart at will at the shoulder 45 soas to give access to the adjustment means that are described below.

The outer support 4 co-operates with the groove 39 and the face 44co-operates with the inner body 6 to guide the inner body in rotationabout the axis 5 without any possibility of relative translation.

To this end, the body 46 carries a cylindrical face 48 of diameterslightly less than that of the face 44, which faces are disposed to faceeach other without mutual contact. The face 48 carries two shoulders 49and 50 which project radially and which are placed respectively facingthe face 44 and facing the groove 39 in which the shoulder 50 isengaged. The shoulder 50 is defined by plane annular faces 51 and 52 andby a cylindrical outer peripheral face 53 sliding over the bottom 40 ofthe groove 39.

The faces 52 and 51 of the shoulder 50 bear respectively against theflanks 41 and 42 via a ball bearing 55, 56. The shoulder 49 is delimitedby plane annular faces 57 and 58 and by a face 59 that is generally inthe form of a circularly symmetrical cylinder about the axis 5, having adiameter substantially equal to that of the face 44 so as to establishfurther guidance of the body 6 and of the support 4 in mutual rotationabout the axis 5 by means of a sliding contact. The face 59 is indentedwith meshing teeth 60 that are regularly spaced apart angularly aboutthe axis 5 for co-operating with manual drive means 61 of conventionaldesign, e.g. as described in Document EP 0 047 190, to co-operate withthe meshing teeth 60 of the body 6 via a gear wheel 62 rotatably mountedon the support 4 about an axis 63 parallel to the axis 5, which gearwheel 62 passes locally through the face 44 of the support 4 towards theaxis 5 via an opening 64 in said face 44.

It may be observed that because of the above-described disposition andwhen the base portion 7 is separated from the head portion 8 at theshoulder 45, the body 6 of the keratotome 3 remains assembled to thehead portion 8 which also carries the manual drive means 61.

Via faces 65, 66, and 67 defining an internal shoulder, the body 6 bearssecurely against two identical and diametrically opposite yokes 68,preferably in a configuration that can be disassembled for maintenancepurposes. Each of the yokes 68 allows a corresponding blade carrier 70to be rotatably mounted about a hinge axis 69 relative to the body 6.The two axes 69 are situated perpendicularly to a common plane 205including the axis 5 and coinciding with the plane marked I--I in FIG.2, the two axes 69 being symmetrically disposed about a plane 204 thatalso includes the axis 5 but that is perpendicular to the plane 205, andthey are situated both as far away as possible from the axis 5 and asclose as possible to the face 58 of the shoulder 49 of the body 6, i.e.from the face 47 of the head portion 48 of the support 4, so as toenable them to be as far away as possible from the base portion 7thereof.

In the plane 205 including the axis 5 and perpendicular to the axes 69,the blade carrier 7 has its own mean longitudinal direction 71perpendicular to the axis 69. It is thus possible to orient it relativeto the axis 5 by pivoting the blade carrier 70 about the axis 69relative to the yoke 68 and to the body 6. In practice, the meandirection 71 specific to each blade carrier 70 intersects the referencesurface 13 within an annular zone 76 thereof that is circularlysymmetrical about the axis 5 having a minimum radius R₃ smaller thanabove-mentioned radius R₂ but nevertheless greater than the transparentzone of a cornea 2.

Means are provided for locking each blade carrier 70 adjustably withrespect to rotation about its axis 69.

To this end, each yoke 68 has a zone 72 that projects approximatelyparallel to the axis 5 relative to the face 52 of the shoulder 50towards the base portion 7 of the support 4, said zone 72 being set backtowards the inside of the support 4 relative to the reference surface 13and not making contact with any portion of the support 4, even thoughsaid zone 72 is situated further from the axis 5 than is the bladecarrier 70.

By means of said zone 72, the yoke 68 carries a ring 73 that isrotatable about an axis 74 but that cannot move in translation alongsaid axis 74. The axis 74 is situated in the plane 205, being offsetrelative to the axis 69 towards the base portion 7 of the support 4, andbeing perpendicular to the direction 71 of the blade carrier 70,relative to which said axis 7 is fixed.

The ring 73 is thus disposed on the opposite side of the zone 72 to theside thereof that faces the axis 5, in a position disengaged by the baseportion 7 of the support 4 when said portion is separated from the headportion 8, thereby enabling mutual rotation to be performed. As shown inFIG. 8, the ring 73 carries graduation marks 80 that are visible whenthe base portion 7 is separated in this way from the head 8, saidgraduations being given in mm, for example, and corresponding toincision diameters. In addition, the zone 72 of the yoke 68 or the bladecarrier 70 itself carries a reference mark 75, e.g. in the form of asingle line.

As shown in FIG. 11, the ring 73 has a micrometer tapping 77 about theaxis 74 and engaging with a coaxial screw 78 securely mounted on theblade carrier 70. By rotating the ring 73, the distance between theblade carrier 70 and the zone 72 of the yoke 68 can be adjusted at theaxis 74, i.e. the orientation of the longitudinal direction 71 of theblade carrier can be adjusted relative to the axis 5, and in particularthe gap or offset R₄ between R₂ and R₃ and extending between the axis 5and the point 79 of intersection between said direction 71 and thereference surface 13 can be adjusted within the limits of the zone 76 onthe reference surface 13. This difference or offset R₄ determines anincision radius.

To make such motion possible, the ring 73 is mounted on the zone 72 ofthe yoke 68 by engaging a circularly symmetrical annular groove 254about the axis 74, as shown in FIG. 11, which groove 254 in the ring 73engages a slideway 81 on the zone 72 of the yoke 68. The slideway 81 isin the form of a fork that is open towards the base portion 7 and thatincludes two arms 250 disposed symmetrically about the plane 205 andthat engage in the groove 254 on either side of the axis 74. Each of thearms 250 is itself split into two branches 251 and 252 towards the baseportion 7, which branches are situated on opposite sides of a plane 253extending approximately perpendicularly to the axis 74 and bearing inopposing manner parallel to said axis 74 in the groove 254. The branches252 closest to the axis 5 are stiff, but the branches 251 furthest fromthe axis 5 have dimensions (as are easily determined by the personskilled in the art given the material from which the yoke 68 is made andsuitably chosen for this purpose by said person skilled in the art) soas to be resilient in a manner that enables the two branches 251 and 252to be permanently prestressed with respect to moving towards each otherin the groove 254. While preventing the ring 73 from moving parallel tothe axis 74 relative to the zone 72 of the yoke 68, and moreparticularly relative to the stiffer branches 252 of the arms 250, sucha disposition makes it possible for the ring 73 to move relative to theaxis 69 and it also enables the ring 73 to tilt abut the zone 72 of theyoke 68.

Each blade carrier 70 is generally tubular in shape, being circularlysymmetrical about its own elongate direction 71 and it delimits aninternal channel 208 that slidably receives a blade 82 for sliding alongits own longitudinal direction 71, said blade extending in rectilinearmanner from a sharp end or tip 83 in the form of a lancet, as shown inFIG. 9 and directed towards the base portion 7, to a drive end 84 thatprojects out from the body 6 and the support 4 in the head portion 8thereof. Respective flats 85 and 86 on the blade 82 and on the bladecarrier 70 prevent relative rotation about the longitudinal axis 71which also constitutes a mean longitudinal axis for the blade 82 passingthrough its tip 83.

The end 84 of each blade 82 co-operates with the corresponding bladecarrier 70 via means 87 enabling the blade 82 to be displaced incontrolled manner in translation along its own longitudinal direction 71relative to the blade carrier 70 between two limiting positions:

a rest position in which the blade is shown in FIG. 1, where the bladeis retracted into the body 6 and the support 4 in the direction of arrow202 along its longitudinal direction 71 so as to be set back from thereference surface 13 with which the tip 83 then lies flush; and

a cutting position shown diagrammatically in FIG. 1 by means ofdot-dashed lines, where the tip 83 projects out from the body 6 and thesupport 4 in the direction of arrow 203 opposite to arrow 202 andrelative to the reference surface 13 which the blade 82 then cuts whilekeeping to the adjusted offset R₄ relative to the axis 5, the magnitudeof said projection being adjustable by acting on means 87 which areindependent for each of the blades 82.

To this end, the end 84 of each blade 82 carries an adjustment knob 88that projects beyond the blade carrier 70 at its end opposite from itstip 83. The knob 88 is rotatably mounted about the longitudinal axis 71of the blade 82 and is secured in translation relative to the bladecarrier 70 in said longitudinal direction 71. The knob 88 carriesgraduations 89 that are expressed, for example, in tenths of amillimeter, said graduations corresponding to the extent whereby the tip83 of the blade 82 projects relative to the reference surface 13 when inits cutting position.

The knob 88 carries a thread 90 whereby it engages in tapping 91 in asleeve 92 mounted to move in translation along the longitudinal axis 71both relative to the adjustment knob 88 and relative to the bladecarrier 70. The sleeve 92 thus locally surrounds the knob 88 over itsthread 90 and also locally surrounds a length 93 of the blade 82situated between the head portion 8 of the support 4 and the end 84.

The sleeve 92 can move in translation along the longitudinal axis 71relative to the blade carrier 70 and also relative to the knob 88 and tothe blade 82, however it is prevented from rotating relative to theblade carrier 70 by keying 94 in an end zone 95 of the blade carrier 70surrounding the sleeve 92, and projecting from the head portion 8 of thesupport 4 in the direction 202 between the end 84 of the blade 82 andthe axis 69.

To co-operate with the graduations 89 of the adjustment knob 88, thesleeve 92 carries a reference 97 on a ring 96 that surrounds the driveknob 88, which reference 97 may be in the form of a radial line relativeto the longitudinal direction 71, as shown in FIG. 10, thereby making itpossible to identify the relative angular position between theadjustment knob 88 and the sleeve 92, i.e. also the blade carrier 70,about the longitudinal direction 71, i.e. making it possible to displaythe amount the tip 83 of the blade 82 projects relative to the referencesurface 13 when the blade 82 is in its cutting position. The end zone 95of the blade carrier 70 surrounds the outside of the sleeve 92, and acompression spring 98 interposed thereby at this level and prestressedin the longitudinal direction 71 tends to urge the sleeve 92 resilientlyin translation along the longitudinal direction 71 relative to the bladecarrier 70 towards the axis 69 and towards the inside of the support 4,i.e. in the direction 203.

Between the end zone 95 of the blade carrier 70 and the adjustment knob88, the outside of the sleeve 92 has an annular shoulder 99. Thisshoulder faces in the direction 203 towards the axis 69 and it bears insaid direction against an opposing shoulder 100 inside a trip knob 101surrounding the sleeve 92 away from the end zone 95 of the blade carrier70, with the trip knob 101 being free to rotate about the longitudinaldirection 71 relative to the sleeve 92 and being also free to move intranslation along said longitudinal direction 71, said motionnevertheless being restricted to limit set firstly by mutual contactbetween the shoulders 99 and 100, and secondly by maximum compression ofthe spring 98.

Facing each other, the trip knob 101 and the blade carrier 70 themselveshave mutual abutment means in the zone 95 in the longitudinal direction71, thereby enabling two stable relative positions to be taken up insaid longitudinal direction 71 depending on the relative angularposition thereof about said longitudinal direction.

More precisely, towards the end zone 95 of the blade carrier 70 in thedirection 203, the trip knob 101 has alternating radial ribs 102 andgrooves 103, the ribs 102 having end flats 104 in the direction 203 thatextend perpendicularly to the longitudinal direction 71. The end zone 95of the blade carrier 70 has alternating radial ribs 105 and grooves 106towards the trip knob 101 in the direction 202, which ribs and groovesare complementary to the grooves 103 and ribs 102, the ribs 105 havingplane end flats 107 in the direction 202 that extend perpendicularly tothe longitudinal direction 71.

The blade 82, the blade carrier 70, the adjustment knob 88, the sleeve90, and the trip knob 101 are dimensioned in a manner that is easilydetermined by the person skilled in the art such that:

when the respective flats 104 and 107 of the ribs 102 and 105 are placedso as to bear mutually against each other in the longitudinal direction71 and with the adjustment knob 88 oriented so that the digit zero isdisplayed on the graduations 89 in association with the reference mark97 of the sleeve 92, the blade 82 is placed in a position such that itstip 83 is set back from the reference surface 13 by an amount such thatshould the ribs 102 subsequently be brought into coincidence with thegroove 106 and the ribs 105 be brought into coincidence with the grooves103 by rotating the trip knob 101, then the effect of the spring 98 isto cause the trip knob assembly 101, the sleeve 92, the adjustment knob88, and the blade 82 to move in translation in the direction 203relative to the blade carrier 70 through an amplitude such that the tip83 comes flush with the reference surface 13, as shown in FIG. 1; and

by placing the trip knob 101 so that it presses again against the endzone 95 of the blade carrier 70 via the flats 104 and 107, and if theadjustment knob 88 then displays the maximum intended extension for thetip 83 of the blade 82 relative to the reference surface 93 (by means ofthe graduations 89 and the reference marks 97), then the tip 83 remainsset back relative to the reference surface 13 until rotation is appliedto the trip knob 101 such that its ribs and grooves correspondrespectively with the grooves and ribs of the end zone 95 of the bladecarrier 70, where upon the spring 98 causes the trip knob 101, thesleeve 92, the adjustment knob 88, and the blade 82 to move suddenly inthe direction 203 relative to the blade carrier 90 until the tip 83 ofthe blade 82 is caused to project from the reference surface 13 by anamount that corresponds to the value displayed by means of theadjustment knob 88.

Thus, prior to placing the keratotome 3 on the anterior face 1 of thecornea 2, the surgeon can adjust the offset R₄ of the intersectionbetween the longitudinal direction 71 and the reference surface 13relative to the axis 5 by means of the ring 73, and this can be doneindependently for each of the blades 82, while the head portion 7 isdisassembled from the body portion 8, after which these two portions canbe reassembled, thereby enabling the surgeon to use the adjustment knob88 to set independent incision depths for the blades 82 while theseblades 82 remain in a rest position, i.e. set back from the referencesurface 13. After disposing the apparatus on the anterior face of thecornea 2 with the axis 5 thereof coinciding with the visual axis, andafter locking it in place by establishing suction in the cavity 9 or byengaging the teeth 31 against the cornea, the surgeon can cause each ofthe blades 82 to move suddenly into its preadjusted projecting positionrelative to the reference surface 13 merely by rotating the trip knobs101, in other words the surgeon can cause each blade 82 to penetrate toa preadjusted depth into the cornea 2.

Thereafter, by acting on the drive means 61, the surgeon causes the body6 to rotate relative to the support 4, thereby giving rise to identicalrotation of the two blades 82 about the visual axis and relative to thecornea 2, i.e. the surgeon can make arcuate incisions having the sameangular length.

In order to enable the surgeon to monitor, and preferably to preadjust,both the angular position of the arcuate incisions and the angularmagnitude thereof, the keratotome 3 of the invention includes means fordetermining the relative angular position of the support and the bodyabout the axis 5, which means 108 are described below with reference toFIGS. 1, 2, and 3, as implemented in a preferred embodiment.

In this embodiment, said means 108 comprise, in particular, in the headportion 8 of the support 4 a coaxial ring 109 which is secured theretobut with the possibility of having its angular position adjusted.

To this end, the ring 109 (which is made of spring steel or the like)has a cylindrical outer peripheral face 110 of a diameter that isidentical to the diameter of the face 44 when said ring is assembled tothe support 4, with the face 110 of the ring 109 then coming into theimmediate proximity of the face 58 of the shoulder 49 of the body 6 allthe way to the face 47. The ring 109 also projects above the face 47. Ata level that corresponds substantially to the level of the face 47, theface 110 is hollowed out in the form of a continuous annular groove 111that engages on a continuous annular rim 112 on the support 4, which rimprojects from the face 44 towards the axis 5 where said face 44 engagesthe face 47.

The ring 109 is axially defined by a plane annular face 113, and by acircular edge 114 that connects to the face 113, and by an insideperipheral face 116 which is essentially in the form of a tapering bodyof revolution about the axis 5, except locally, as explained below.

The ring 109 has a discontinuity in the form of a gap 117, therebymaking it elastically compressible radially, and it is mounted relativeto the support 4 so that its face 110 comes into abutment against theface 44 of the support 4, which thus constitutes a friction bearingsurface therefor.

However, when voluntary manual force is applied to the ring 109 in acircumferential direction so as to tend to close the gap 117, then thediameter of the face 110 of the ring 109 is reduced, and consequently itcan be rotated at will about the axis 5 relative to the support 4 beforebeing secured thereto again by releasing said manual force.

In order to enable such force to be applied, the portion of the ring 109that projects relative to the face 47 of the support 4 on either side ofthe gap 17 has manual grasping means in the form of two notches 108 thatleave a lug 119 between themselves and the gap 117, thus providing thesurgeon's fingers with purchase towards the gap 117.

In an inner peripheral zone 120 that does not include the gap 117 andthat extends over an arc α₃ of 180°, the frustoconical inner peripheralface 116 is not directly connected to the face 113 of the ring 109, withsuch connection occurring via an inner peripheral face 121 that iscircularly cylindrical about the axis 5 and towards which said face 121faces. At beth ends, relative to a circumferential direction centered onthe axis 5, the face 121 connects via an abutment shoulder 122 to thefrustoconical inner peripheral face 116.

In addition, the body 6 carries two abutment tabs 124 projectingparallel to the axis 5 on the face 58 of the shoulder 49 and in themanner that is adjustable within a zone of said face 58 that remainsdisengaged by the ring 109. The abutment tabs 124 are placed to face theinner peripheral zone 120 of the ring 109 and are suitable for comingcircumferentially into abutment against one or other of shoulders 122 ineither direction of rotation 206 or 207 of the body 6 relative to thesupport 4. These abutment tabs 124 are symmetrical about the plane 204from which they are each offset by less than 90°, respectively in thedirection 206 and in the direction 207.

To this end, the face 58 of the body 6 has a plurality of identicalblind holes 125 that are circularly cylindrical about respective axes126 uniformly distributed about the axis 5 and equidistant therefrom,and each of the blind holes 125 is suitable for receiving one of theabutment tabs 124; in the preferred example as shown, there are thirteenblind holes 125 which are symmetrically distributed about the plane 204at an angular pitch of α₄ equal to 10° over a total angular extent of120°; for example, each hole 125 is tapped, and each tab 124 is providedwith a threaded rod 127 suitable for being screwed into a hole 125.

By securing the two tabs 124 to the body 6 in angular positions that aresuitably chosen relative to the axis 5 and that are symmetrical aboutthe plane 204, and insofar as each tab 124 is suitable for comingcircumferentially into abutment against one of the shoulders 122 in thedirection 206 or 207 of rotation of the body 6 relative to the support4, rotation limits for the body 6 about the axis 5 relative to thesupport 4 can be fixed firstly with predetermined amplitude of relativerotation between the directions limited by adjusting the angularposition of the tabs 124 on the body 6, and secondly with the angularpositioning of said limiting orientations being adjusted relative to thesupport 4 by adjusting the angular position of the abutment shoulders122 of the ring 109 relative thereto.

In this respect, the blind holes 125 act as graduations relative to thebody 6 enabling the angular position of the body to be observed relativeto the ring 109, i.e. relative to the support 4, in co-operation withthe abutment shoulders 122 of the ring 109. Each of these blinds holes125 is preferably also associated with a graduation 123 which, in thepresent example, is expressed as the value of the angular offset betweenthe axis 126 of the blind hole 125 in question about the axis 5 andrelative to the plane 205, said value being expressed in degrees. Thus,a blind hole 125 whose axis 126 lies in the plane 204 carries the number90 as a graduation 123, and the blind holes 125 that follow one anotherin succession from said blind hole 125 on either side of the plane 204carry the numbers 80, 70, 60, 50, 40, and 30, respectively.

Before causing the blades 82 to move suddenly from their rest positionsto their cutting positions, but after securing the keratotome 3 in anappropriate position on the anterior face 1 of the cornea 2, it sufficesfor the surgeon to use the means 61 to bring the body 6 into anorientation such that one of the tabs 124 is in abutment against thecorresponding shoulder 122, and then after causing the blades to beextended suddenly, the surgeon causes the body 6 to rotate relative tothe support 6 until the other tab 124 comes into abutment against theother shoulder 122, thereby ensuring that incisions are made ofpredetermined angular amplitude, and also in positions that are likewisepredetermined.

In order to facilitate the prior adjustments, the body 6 preferably alsoincludes means 128 for identifying an axis of astigmatism, e.g. in amanner suitable for removably securing to the body 6, at the same timeas that one of the abutment tabs 124 which is offset in the direction206 relative to the plane 204 in the example shown. This may be done byclamping said tab and the face 58 of the shoulder 49 of the body 1together such that said adjustment means lie in a common plane thatincludes the axis 5 and the common axis 126 of said tab 124 and of thehole 125 that receives it; which plane coincides with the planereferenced IX--IX in FIG. 2.

In particular, FIGS. 2, 6, and 7 show means 128 for marking anastigmatism axis and designed in the above manner. These means areprovided in the form of a needle 129 which (as shown in FIG. 7)converges towards the axis 5 in a direction running from the headportion 8 towards the foot portion 7, while remaining fully set backrelative to the reference surface 13.

Towards the axis 5 and towards said reference surface 13, the needle 129has a bend terminated by a free pointed end 130 which terminates at theaxis 5 in the vicinity of the surface 13 of the reference, such thatsaid point constitutes the reference mark to be superposed on the markidentifying the visual axis of the patient, whereas at the opposite endit is securely imprisoned by another end 131 in an intermediate assemblypart 132 suitably shaped to locally engage the faces 65, 67, 66 of thebody 6 and also the face 58 of the shoulder 49 thereof, with this takingplace in a forked zone 133 suitable for inserting between the respectivetab 124 and the face 58, around the rod 127 of said tab 124.

Under such conditions, the angular length of each incision and theangular position thereof can be adjusted as follows, it being assumedthat the depth and the diameter of the incision are already adjusted andeach of the blades being assumed to be in its rest position:

the angular extent of each of the incisions to be made is determinedwith reference to the visual axis;

respective tabs 124 are screwed into those two holes 125 whosegraduations 123 correspond to one-half of the angular extent selectedfor the incision, by fixing the means 128 by means of the tab 124 offsetin the direction 206 about the plane 104;

the ring 109 is rotated relative to the support 4 so as to bring the tab124 provided with the means 128 into contact with the associatedabutment shoulder 122 without rotating the body 6 relative to thesupport 4;

after the keratotome has been appropriately placed and secured on thecornea, in particular by bringing the tip 130 into coincidence with themark specifying the visual axis of the patient, and by orienting themanual control means 61 in a manner that is convenient for the surgeon,the ring 109 and the body 6 may optionally be rotated simultaneouslyrelative to the support 4 while maintaining the above-mentioned contactbetween the tab 124 provided with the means 128 and the associatedabutment shoulder 122, thereby bringing the needle 129 into coincidencewith the astigmatism axis as previously marked on the anterior face 1 ofthe cornea 2;

the blades are caused to move into their cutting positions, and withoutrotating the ring 109 relative to the support 4, the body 6 is caused torotate relative thereto in the direction 207 until the other one of thetabs 124 comes into contact with the other one of the shoulders 122,thereby causing the desired incisions to be made; and

the blades are retracted to their rest position and the keratotome isseparated from the cornea.

In the example shown in FIG. 2, in particular, two arcuate incisions arethus made simultaneously each over an angular extent of 120°, and eachuniformly distributed on either side of the axis of the astigmatism, byplacing the two tabs 124 in the blind holes 125 that are marked by thenumbers 60 constituting graduations 123, and in the embodimentdescribed, the keratotome of the invention thus makes it possible toperform a range of incisions having respective angular extents lying insteps of 20° between 60° (in which case the tabs 124 must be placed inthe blind holes 125 marked with the number 30), and 180° (in which casea single tab 124 must be placed in the blind hole 125 marked by thenumber 90), but without going beyond the ambit of the present inventionother ways of varying the angular extent of the incisions that can bemade using a keratotome of the invention are available, as are otherlimit values on said angular extent.

What is claimed is:
 1. A keratotome for making an incision in a cornea,and comprising, for this purpose:an envelope-forming tubular outersupport having a determined axis and including, for application againsta cornea, an annular base portion that is circularly symmetrical aboutthe axis of the support and that defines a reference geometrical surfacedetermined by the shape presented by the cornea when the support has itsbase portion pressed thereagainst; a tubular inner body disposedcoaxially inside the support and set back towards the inside of thesupport relative to the reference surface; guide means for guiding thebody in rotation about the axis relative to the support; drive means fordriving the body in rotation about the axis relative to the support; atleast a blade disposed inside the body and extending along alongitudinal direction, the blade having a sharp tip in a determineddirection relative to its longitudinal direction; and means forproviding a connection between the blade and the body, said meansincluding means for displacing the blade in controlled manner intranslation along its longitudinal axis relative to the body between arest position, in which it is set back towards the inside of the supportrelative to the reference surface, and in which the tip is directedtowards said reference surface, and in a cutting position where the tipprojects outside from the support relative to the reference surface, ina manner that is offset relative to the axis of the support; wherein, inorder to perform arcuate incisions of determined angular position and ofdetermined angular length, the support and the body have determiningmeans for determining their relative angular position which includeabutments defining two limiting relative angular positions between thesupport and the body and carried respectively by the support and by thebody.
 2. A keratotome according to claim 1, wherein the determiningmeans include graduation forming means forming graduations for markingangular position relative to the support and the body and carriedrespectively by the support and by the body.
 3. A keratotome accordingto claim 1, wherein the support carries a coaxial ring that is angularlyadjustable in position and that carries said abutments that are integraltherewith and that are offset by 180° from each other, and wherein saidabutments carried by said body are angularly adjustable independently.4. A keratotome according to claim 3, wherein the body carries means formarking the axis of astigmatism which are integral with one of saidabutments.
 5. A keratotome according to claim 3, wherein said ring isopened by a radial gap, which is elastically compressible radially andin centrifugal radial abutment against a coaxial annular bearing surfaceof the support under prestress such that it is temporarily secured tothe support by friction, but with the gap nevertheless remaining open,and wherein it has grasping means on respective sides of said radial gapfor the purpose of enabling manual force to be applied circumferentiallyin such a direction as to close the gap.
 6. A keratotome according toclaim 1, wherein:another blade angularly is offset by 180° relative tothe first blade and disposed inside the body along its own axialdirection and having its own sharp tip in a determined direction alongits longitudinal direction; and wherein link means between said otherblade and the body themselves include means for displacing the otherblade in adjustable manner in translation along its own longitudinaldirection relative to the body between a rest position in which saidother blade is set back towards the inside of the support relative tothe reference surface, and in which its tip points towards saidreference surface, and a cutting position in which said tip projects outfrom the support relative to the reference surface so as to be offsetrelative to the axis of the support.
 7. A keratotome according to claim6, wherein the means for displacing each of the blades in adjustablemanner in translation along its own longitudinal directioncomprise:means for displaying the adjusted value of said projectionwhile the blade remains in its rest position; and means for causing theblade to move voluntarily and suddenly from its rest position to itscutting position.
 8. A keratotome according to claim 7, wherein saidmeans for displacing each blade in adjustable manner in translationalong its own longitudinal direction comprise:a blade carrier attachedto said body; an adjustment knob placed to project beyond said bladecarrier away from the tip and mounted to rotate about said longitudinaldirection relative to the blade carrier, and constrained to move intranslation with the blade along said longitudinal direction; a sleevemounted to move in translation relative to the adjustment knob andrelative to the blade carrier, along said longitudinal direction, andconstrained to rotate with the blade carrier about said longitudinaldirection, and having a transverse shoulder extending transverselyrelative to said longitudinal direction and facing in a direction goingfrom the rest position towards the cutting position; threaded connectionmeans between the adjustment knob and the sleeve; micrometer graduationsfor identifying the relative angular position of the adjustment knob andof the sleeve about said longitudinal direction, and constituting meansfor displaying the adjusted value of said projection; means forresiliently urging the sleeve in translation relative to the bladecarrier along said longitudinal direction in a direction going from therest position towards the cutting position; a trip knob mounted torotate relative to the adjustment knob, to the sleeve, and to the bladecarrier, and having a shoulder extending transversely relative to saidlongitudinal direction and facing in a direction going from the cuttingposition towards the rest position, and bearing against said transverseshoulder of the sleeve; and mutual abutment means between the trip knoband the blade carrier in said longitudinal direction, comprising on thetrip knob alternating radial ribs and grooves about said longitudinaldirection and facing in a direction going from the rest position towardsthe cutting position, and on the blade carrier alternating radialgrooves and ribs about said longitudinal direction, and facing in adirection going from the cutting position towards the rest position, andrespectively complementary to the ribs and the grooves of the trip knob,said ribs and grooves being shaped so that mutual thrust between thetrip knob and the blade carrier by means of said ribs as by engagementof said ribs in said grooves is stable.
 9. A keratotome according toclaim 8, including means for adjusting the offset value of the tip ofeach blade relative to the axis of the support in the cutting position,which means comprise:hinge means for hinging the blade carrier to thebody about a determined hinge axis offset relative to the axis of thesupport and set back towards the inside of the support relative to thereference surface, and perpendicular to the longitudinal direction ofthe blade and to a plane including the axis of the support; and meansfor locking the blade carrier relative to the body in adjustable mannerin rotation about the hinge axis.